1. Field of the Invention
The present invention relates to a cylinder identification apparatus for an internal combustion engine installed on a vehicle such as a motor vehicle, and more particularly to such a cylinder identification apparatus as can be applied to an internal combustion engine that is controlled at variable valve timing.
2. Description of the Related Art
FIG. 16 is a block diagram that shows the configuration of this kind of conventional cylinder identification apparatus for an internal combustion engine disclosed in Japanese Patent Application Laid-Open No. 8-277744 for instance. FIG. 17 is a view that shows the configuration of each signal detector in FIG. 16. FIG. 18 is a waveform diagram that shows one example of each of a first signal sequence and a second signal sequence in FIG. 16.
In these figures, a camshaft 1 with a speed reduction ratio of xc2xd with respect to a crankshaft 11 of the internal combustion engine is driven to rotate by and in synchronization with the crankshaft 11 through a belt drive mechanism or the like. A first signal detector 81 for generating a first signal sequence POSR related to the rotation of the crankshaft 11 includes a rotating disk 12 integrally mounted on the crankshaft 11, a multitude of projections or teeth 81a formed at a first prescribed angular interval (e.g., crank angle of 1xc2x0-10xc2x0) along the outer periphery of the rotating disk 12, and a sensor 81b of the magnetic pickup type, the Hall effect type, the magneto-resistance type, etc., arranged in the vicinity of the outer periphery of the rotating disk 12 for sensing each projection 81a when its sensing portion comes to face therewith.
The first signal sequence POSR includes a crank angle signal generated at each first prescribed angle or angular interval in synchronization with the rotation of the crankshaft 11, and a reference position signal generated at each second prescribed angle or angular interval (e.g., crank angle of 360xc2x0) and corresponding to a reference position of a specific group of cylinders (in this case, cylinder #1 and cylinder #4 to be concurrently controlled) of the internal combustion engine.
The projections 81a corresponding to the respective pulses of the crank angle signal in the first signal sequence POSR includes an untoothed or lost teeth portion 80 (see FIG. 17) in the form of an angular range (i.e., a range where there exists no projection 81a) in which no crank angle signal is continuously generated over a crank angle of ten degrees to several tens degrees. An end position of the untoothed portion 80 (i.e., the position at which the next angle signal begins to be generated) corresponds to the reference positions xcex8R of the specific cylinder group. The untoothed portion 80 is arranged at one location (i.e., every crank angle of 360xc2x0) on the rotating disk 12 formed integral with the crankshaft 11.
A second signal detector 82 for generating a second signal sequence SGC related to the rotation of the camshaft 1 includes a rotating disk 2 integrally mounted on the camshaft 1, projections 82a formed on and along the outer periphery of the rotating disk 2 at locations corresponding to the respective cylinders (in this case, four cylinders), and a sensor 82b in the form of an electromagnetic pickup arranged in the vicinity of the outer periphery of the rotating disk 2 for sensing each projection 82a when its sensing portion comes to face therewith.
In this case, the second signal sequence SGC consists of a train of pulses of a cylinder identification signal corresponding to the respective cylinders. The pulse width PW1 of a pulse of the cylinder identification signal corresponding to a specific cylinder (cylinder #1) differs from and is longer than the pulse widths PW2-PW4 of pulses corresponding to other cylinders. The first and second signal sequences POSR and SGC are input to a microcomputer 100 through an interface circuit 90.
The microcomputer 100 constitutes a control means for controlling parameters of the internal combustion engine. The microcomputer 100 includes a reference position signal detection means 101 for detecting a reference position signal related to the specific cylinder group from the first signal sequence POSR, a reference position detection means 101A for detecting the reference position of each cylinder based on the angle signal in the first signal sequence POSR and the reference position signal, a cylinder group identification means 102 for identifying cylinder groups based on the reference position signal, a cylinder identification means 103 for identifying each cylinder based on the ratio of generation times or durations of successive signal pulses in the second signal sequence SGC (cylinder identification signal), a control timing calculation means 104 for counting the number of angle signal pulses included in the first signal sequence POSR and calculating the control timing of control parameters P (ignition timing, etc.), and an abnormality determination means 105 for determining whether there is abnormality (or failure) in one of signal sequences POSR and SGC and outputting an abnormality determination signal E to the cylinder identification means 103 and the timing calculation means 104 when it is determined that one of the signal sequences POSR and SGC is abnormal.
Here, note that the cylinder identification means 103 identifies each cylinder based at least on the second signal sequence SGC, and the control timing calculation means 104 calculates the control timing of the control parameters P based at least on the cylinder identification result of the cylinder identification means 103 and the second signal sequence SGC.
For instance, when the first and second sequences POSR and SGC are normal, the cylinder identification means 103 measures the generation duration or range of each cylinder identification signal included in the second signal sequence SGC by counting pulses of the angle signal included in the first signal sequence POSR, so that it identifies each cylinder based on the measurement result, as will be described later. On the other hand, upon occurrence of abnormality (e.g., when there is obtained no first signal sequence POSR), the cylinder identification means 103 identifies each cylinder based on the calculation of the ratio of generation times or durations of successive pulses of the cylinder identification signal (e.g., duty ratio of adjacent or successive high (H) level and low (L) level ranges) by using only the second signal sequence SGC in response to an abnormality determination signal E, thus making it possible to perform backup control.
Similarly, when the first and second sequences POSR and SGC are normal, the control timing calculation means 104 calculates the control timing of the parameters P by using the reference position signal included in the first signal sequence POSR and the cylinder identification signal included in the second signal sequence SGC, and by counting the crank angle signal. In addition, upon occurrence of abnormality (e.g., when there is obtained no first signal sequence POSR), the control timing calculation means 104 performs the backup control by using only the second signal sequence SGC in response to an abnormality determination signal E. Moreover, when the second signal sequence SGC is not obtained, the control timing calculation means 104 performs the backup control through simultaneous ignition of each cylinder group or the like by using only the cylinder identification result of the cylinder group identification means 102 based on the first signal sequence POSR.
Incidentally, note that at normal time, the control timing calculation means 104 determines the control parameters P such as the ignition timing, the amount of fuel to be injected, etc., through calculations using a map for example, based on engine operating condition signals D from various sensors (not shown), and supplies them to the respective cylinders.
Next, the operation of the conventional apparatus shown in FIG. 16 and FIG. 17 will be explained while referring to FIG. 18. First of all, the rotating disk 12 with the projections 81a formed at the first prescribed angular interval is mounted on the crankshaft 11, and the sensor 81b is arranged in opposition to the projections 81a. In this manner, the first signal detector 81 is constructed such that it generates the first signal sequence POSR including the angle signal and the reference position signal.
At this time, the untoothed or lost tooth portion 80 is provided at a part of the projections 81a (e.g., at one location on the rotating disk 12 in case of a four-cylinder engine) in order that not only the angle signal but also the reference position signal corresponding to each cylinder group is included in the first signal sequence POSR.
The untoothed portion 80 is detected by the sensor 81b that converts the presence or absence of a projection 81a into the first signal sequence POSR (electrical signal). Subsequently, an L level range xcfx84 (corresponding to the untoothed portion 80) included in the first signal sequence POSR is detected by the reference position signal detection means 101 in the microcomputer 100 based on the magnitude of each pulse generation period or cycle.
As a result, the first signal sequence POSR (see FIG. 18), which is generated in correspondence to the projections 81a as the crankshaft 11 rotates, includes the crank angle signal that consists of a train of pulses generated every first prescribed angle (e.g., crank angle of 1xc2x0) and the reference position signal generated every crank angle of 360xc2x0 that consists of an L level range (e.g., a range in which no crank angle signal is obtained over only a prescribed angular interval from a crank angle of ten degrees to several tens degrees) corresponding to the untoothed portion 80.
Here, note that the end position of each L level range xcfx84 (i.e., the position at which the following crank angle signal begins to be generated) becomes the reference position xcex8R used for the calculation of the control timing of the specific cylinder group. Accordingly, the cylinder group identification means 102 identifies the specific cylinder group and other cylinder groups based solely on the reference position signal from the reference position signal detection means 101, so that the control timing calculation means 104 can quickly identify groupwise ignitable cylinder groups. As a result, the minimum internal combustion engine control performance can be obtained.
In addition, the second signal sequence SGC generated in correspondence to the projections 82a on the rotating disk 2 mounted on the camshaft 1 includes the cylinder identification signal in which the pulse width PW1 of the pulse corresponding to the specific cylinder (cylinder #1) is set longer than that of pulses corresponding to other cylinders so that the cylinder identification means 103 can identify the specific cylinder and the other cylinders, and the control timing calculation means 104 can obtain the desired internal combustion engine control performance based on the cylinder identification result.
At this time, in cases where the first and second signal sequences POSR and SGC are soundly or correctly obtained, the cylinder identification means 103 measures the pulse width of each signal pulse in the second signal sequence SGC by counting the number of pulses of the crank angle signal in the first signal sequence POSR, whereby it identifies the specific cylinder and the other cylinders.
On the other hand, in cases where no first signal sequence POSR is obtained due to a failure of the sensor 81b, etc., on the crankshaft 11 side (i.e., when the first signal sequence POSR always indicates a constant level or an abnormal pulse width), the abnormality determination means 105 generates an abnormality determination signal E, which is then input to the cylinder group identification means 102, the cylinder identification means 103 and the control timing calculation means 104. As a consequence, the cylinder identification means 103 performs cylinder identification by using the second signal sequence SGC alone, thereby enabling the backup control of the control parameters P for the internal combustion engine.
That is, the ratios between the cycle or period of an H level and that of an L level of pulses of the second signal sequence SGC are successively calculated and compared with each other, whereby the specific cylinder pulse of the pulse width PW1 having the largest H level period or range is identified, thus determining the specific cylinder. Thereafter, the other cylinders are sequentially identified based on the specific cylinder pulse. At this time, for instance, by making the fall timing of each pulse of the second signal sequence SGC the ignition timing of each cylinder, it is possible to provide the minimum internal combustion engine control performance.
In addition, when the second signal sequence SGC is not obtained due to a failure of the sensor 82b, etc., on the camshaft 1 side, the control timing calculation means 104 performs the backup control in accordance with simultaneous ignition control or the like based solely on the cylinder group identification result according to the reference position signal in the first signal sequence POSR. In this manner, the minimum internal combustion engine control performance can be obtained.
The first signal detector 81 for detecting the first signal sequence POSR including the crank angle signal and the reference position signal is provided on the crankshaft 11 side, and the second signal detector 82 for detecting the second signal sequence SGC including the cylinder identification signal is arranged on the camshaft 1 side, so that the crank angle and the reference position xcex8R can be accurately detected without generating a phase difference or shift between the camshaft 1 and the crankshaft 11 that drives the camshaft 1 due to the interposition of a transmission mechanism such as a belt and pulley transmission mechanism therebetween. Consequently, it is possible to accurately control the ignition timing and the amount of fuel to be injected to each cylinder.
In addition, by setting a reference position signal for the specific cylinder group, the specific cylinder group can be identified every time a reference position xcex8R is detected so that all the cylinder groups can be detected quickly and easily. Thus, the ignition timing control and the fuel injection control particularly upon engine starting can be performed quickly and appropriately.
Moreover, even when the first signal sequence POSR is not obtained due to a failure of the first detector 81, etc., the cylinders and the control reference position can be identified by calculating the ratios of the successive cycles or periods of pulses of the second signal sequence SGC, whereby the ignition timing control and the fuel injection control can be continued without stopping the internal combustion engine (i.e., backup control being able to be performed).
Although in the above-mentioned explanation, the pulse width PW1 of the specific cylinder is made different from those of the other cylinders as a difference in the pulse form of the cylinder identification signal between the specific cylinder and the other cylinders, only the pulse corresponding to the specific cylinder may be superposed in phase on the reference position signal so that the specific cylinder can be identified based on the level of the second signal sequence SGC at each reference position xcex8R.
FIG. 19 is a waveform diagram showing an operation when the pulse of the cylinder identification signal corresponding to the specific cylinder is superposed on the phase of the reference position signal. Here, note that the pulse width PW1 of the pulse corresponding to the specific cylinder is set to be longer than the pulse width of each of the other cylinders. If, however, the phase of the pulse of the cylinder identification signal corresponding to the specific cylinder is superposed on the phase of the reference position signal, the pulse width of the cylinder identification signal corresponding to the specific cylinder may be the same as the pulse width of the other cylinders.
In FIG. 19, the phase of the second signal sequence SGC for the specific cylinder (cylinder #1) is superposed on the phase of the reference position signal included in the first signal sequence POSR, and becomes an H level at a corresponding reference position xcex8R. On the other hand, the phases of pulses of the second signal sequence SGC corresponding to the other cylinders are not superposed on the phase of the reference position signal, and hence become an L level at corresponding reference positions xcex8R.
That is, the pulse of the cylinder identification signal corresponding to the specific cylinder (cylinder #1) indicated by the pulse width PW1 is at an H level over a range including an L level range xcfx84 of the first signal sequence POSR, whereas the pulses of the cylinder identification signal corresponding to the other cylinders (cylinder #3, cylinder #4 and cylinder #2) become an H level immediately after corresponding reference positions xcex8R obtained from the first signal sequence POSR.
Accordingly, it is understood that if the second signal sequence SGC is at an H level at a reference position xcex8R, it corresponds to the pulse of the specific cylinder, whereas if it is at an L level, it corresponds to a pulse of any of the other cylinders. As a result, the cylinder identification means 103 identifies the specific cylinder from the level of the second signal sequence SGC at the point in time at which a reference position xcex8R has been detected by the reference position detection means 101A. Thereafter, the other cylinders are sequentially identified based on the specific cylinder.
In addition, identifying the cylinders by referring to the level of the second signal sequence SGC each time the reference position xcex8R is detected can eliminate the need of measuring pulse widths, etc.
Thus, in the past, when the crank angle position signal or the cylinder identification signal has failed or become abnormal, a minimum performance level has been maintained by performing the backup control by the use of another normal signal.
As mentioned above, such a kind of conventional apparatus can carry out cylinder identification quickly by a combination of the reference (crank angle) position signal and the crank angle signal generated in accordance with the rotation of the crankshaft, and the cylinder identification signal generated in accordance with the rotation of the camshaft. Since, however, the phase of the cylinder identification signal and the phase of the reference crank angle position signal are mutually superposed on each other, there arises the following problem. That is, in cases where this apparatus is applied to an internal combustion engine which is equipped with a variable valve timing mechanism, the phase of the cylinder identification signal might not be superposed on the phase of the reference crank angle position signal depending upon a variable cam phase range. As a result, cylinder identification becomes impossible, thus making it unable to perform the backup control.
In addition, in cases where the above-mentioned prior art is intended to be adapted to an internal combustion engine which is equipped with a variable valve timing mechanism, there will be another problem in that the combination of the reference crank angle position signal, the cylinder identification signal and the angle signal becomes complicated.
The present invention is intended to solve the problems as referred to above, and has its object to provide a cylinder identification apparatus of the character as described above which can be applied to an internal combustion engine that is subjected to variable valve timing control without complicating the combination of signals.
Bearing the above object in mind, the present invention resides in a cylinder identification apparatus for a VVT controlled internal combustion engine which includes: a crank angle position signal generator for generating a crank angle position signal including a train of pulses corresponding to rotational angles of a crankshaft of the internal combustion engine and specific signal pulses which are used to obtain a plurality of reference crank angle positions of respective cylinders of the internal combustion engine; and a cylinder identification signal generator for generating a cylinder identification signal including a train of pulses corresponding to the respective cylinders in accordance with the rotation of at least one of an intake-side cam and an exhaust-side cam which are caused to rotate at a ratio of xc2xd with respect to the rotational speed of the crankshaft and move to an advance angle position or a retard angle position under variable valve timing (VVT) control. The apparatus further includes: a reference crank angle position detection part for detecting the plurality of reference crank angle positions based on the specific signal pulse positions of the crank angle position signal; a reference crank angle position identification part for identifying correlation between the plurality of reference crank angle positions and cylinder groups based on a combination of the plurality of reference crank angle positions and the cylinder identification signal; a cylinder identification range setting part for setting cylinder identification ranges of a prescribed angular length with each of the reference crank angle positions as a reference in consideration of an advance angle and a retard angle according to the VVT control; and a cylinder identification part for identifying the cylinders based on the reference crank angle positions whose correlation with the cylinder groups within each of the cylinder identification ranges is specified and the cylinder identification signal.
According to the above arrangement, the cylinder identification apparatus can be applied to a VVT controlled internal combustion engine without complicating the processing of combining the signals upon cylinder identification. Specifically, cylinder identification ranges and signals are set in consideration of valve operation angles (e.g., intake valve operation angle and/or exhaust valve operation angle) so that cylinder identification can be performed irrespective of the valve operation angles.
The above and other objects, features and advantages of the present invention will become more readily apparent to those skilled in the art from the following detailed description of preferred embodiments of the present invention taken in conjunction with the accompanying drawings.